Research has shown that excellent single crystalline silicon thin films can be grown on amorphous silica substrates by light induced zone melting and recrystallization. Adding another layer of thermally insulating silica, silicon oxynitride, or the like, depositing another layer of amorphous or poly silicon (or germanium or silicon germanium alloy, etc.) one can then recrystallize the top layer to achieve a second active layer of electronic material. Iteration of these steps can lead to multiple layers of active electronics.
However, there are problems regarding successful fabrication and use of such arrays. First, heating of the top semiconductor layer may disturb the already created devices in lower layers. Second, during use, performance may be degraded due to heat.